The contact surface treatment of, for example, skis, to improve their performance, is well known in the art. It has been found that the normal smooth bottom on such devices does not produce the best results, such a bottom introducing a viscous drag factor that is undesirable. Efforts to reduce the drag on the surface of the ski that contacts the supporting medium have primarily been directed to creating a three-dimensional surface having a plurality of sloped portions, with the slope oriented in the intended direction of travel of the ski. One example of such a structure is shown in U.S. Pat. No. 3,408,086 of Bennett wherein overlapping scales are formed on the bottom of the ski which function as the contact surface. The scales are sloped to reduce friction or drag. Adjacent scales form a series of groove-like configurations which enhance the directional stability of the ski and enable the operator to exercise a good degree of control, especially in turns. Such a structure however is unusually complex and is subject to compaction of the material over which the ski is moving. This compaction is reduced by not extending the scale pattern all of the way out to the edges of the ski, but at the cost of leaving the edges of the ski untreated. Thus the advantages gained from the treatment are not available for high performance skiing involving numerous turns and rapid changes of direction where the ski edges are called upon to function as contact surfaces.
Variations on the scale construction are shown in U.S. Pat. Nos. 4,323,265 of Benner, 4,178,012 of Roth et al, 3,874,315 of Wright and 2,914,335 of Rivard. Nevertheless, all of the foregoing prior art arrangements rely upon sloping surfaces to decrease friction or drag, which are, in most cases, unduly complex and difficult to form, and are not readily applicable to the ski edges or to the edges of water sports boards such as surf boards, knee boards and wind surfers.
Another approach to reducing drag is based upon the catamaran principle, wherein the contact surface of the ski or other device is formed with two or more longitudinally extending ribs. Such a configuration, examples of which are shown in U.S. Pat. Nos. 3,428,979 of Johnson, 3,761,980 of Silverstein, 3,827,096 of Brownson and 3,077,617 of Steffel, reduces the area in contact with the ski supporting snow or water, thereby reducing drag, and enhances the longitudinal stability of the device. As in the case of the sloping surfaces or scales, there is no treatment of the ski edges. Hence these arrangements are unsuitable for competition or high performance type skis and boards. In addition, these ribs often tend to resist changes in direction, which makes the ski or board unsuitable for competitive use.